3.2 Our current path
Could we meet the Paris Agreement targets (well below 2 °C above preindustrial climate, pursuing efforts for 1.5 °C) just by reducing greenhouse gas emissions and no geoengineering?
The first question is: where are we heading? Current global emissions are close to, or slightly higher than, the RCP8.5 scenario (Figure 6).
If we continue on this very high pathway, our odds of exceeding 4 °C warming this century are about 50–50. In other words, as far from preindustrial climate as the last ice age was in the opposite direction. However, following RCP8.5 would require rapidly increasing emissions and it can be considered a ‘no climate policy’ (or worse) scenario – something that we do not have.
How far would current policies and pledges take us?
The website climateactiontracker.org tracks the effects of policies and pledges on our future climate. Perhaps unsurprisingly, predicted temperatures for pledges are higher than the targets, and those for current policies are higher still.
Visit‘Global’ page. Have these predictions changed at all ?
In December 2019, the predicted temperature under current pledges had actually increased by 0.1 °C, to 2.8 °C, while the lower bound for current policies had decreased by the same amount. The answer for future years is unknown, though both are intended to decrease with time.
Pledges are based on current knowledge: unpredictable aspects – such as technology, energy use and political will – will affect the ability of nations to reduce their emissions. To respond to this the Paris Agreement outlines an iterative approach of re-evaluating and repledging every five years, this is known as a ‘ratchet’ mechanism.